Optical Couplers are typically utilized to separate or combine an optical signal, such as an optic signal in a fiber optic cable. For example, a 1.times.n optical coupler splits a single input signal into n output signals. Conventional optical couplers are comprised of a plurality of fiber optic cables. Where an optical signal is to be split, the number of cables outputting a signal is more than the number of cables inputting the signal. A 1.times.n optical coupler, for example, has one input cable and n output cables. Similarly, where an optic signal is to be combined, the number of cables outputting a signal is less than the number of cables inputting the signal. Typically, a 1.times.n coupler is physically the same as an n.times.1 coupler. All that differs is into which end of the optical coupler the signal is input.
In order to form a conventional optic coupler, several fiber optic cables are fused together. In order to fuse the fibers, the fibers are placed in contact with each other and twisted. The fibers are twisted so that there is strong optical coupling between fibers. Since alignment of the twisted fibers is not controlled, the fibers' position is checked using only the naked eye. The fibers are typically heated and placed under tension by drawing the fibers. In general, the heat source used to heat the fibers is fueled by hydrogen. As the fibers are heated and drawn, the fibers fuse, forming a joint. To obtain a different number of input fibers than output fibers, a portion of each of a predetermined number of fibers is removed.
For example, a conventional 1.times.2 optical coupler would be formed by twisting two optical fibers together. The fibers would then be heated and drawn until the fibers fuse at a joint. A portion of a fiber on one side of the joint would then be removed to form the 1.times.2 coupler.
Two optical coupler properties that are important are uniformity and polarization sensitivity. Uniformity refers to the split in the signal carried by the n fibers in a 1.times.n or n.times.1 coupler. High uniformity, having each of the n fibers carry an equal portion of the signal, is desirable.
Low polarization sensitivity is desired to ensure that the optical coupler performs adequately. All conventional optical couplers are, to some degree, dependent on the polarization state of the input signal. For example, the optical coupler may be more likely to transmit light of a particular polarization through one of the n fibers. There is also currently no acceptable method of controlling the polarization state in an optical fiber. To ensure that the deviations due to the polarization of the signal are minimal, the optical coupler should be insensitive to the signal's polarization.
The conventional method for manufacturing twists the fibers to ensure close proximity and, therefore, fusion of the fibers at the joint. Because the fibers are twisted, the position of each fiber is not well controlled. Consequently, the uniformity of the coupler suffers. En addition, twisting the optical fibers also causes the coupler to be more sensitive to the polarization of the optical signal.
Accordingly, what is needed is a system and method for providing a high uniformity, low polarization sensitivity optical coupler. The present invention addresses such a need.